The nodulus and uvula of the vestibulo-cerebellum appear to play an important role in controlling a process in the vestibular system that is responsible for producing its dominant time constant and low frequency characteristics. We have termed this process "velocity storage" because it stores or holds activity related to head velocity and to the velocity of slow phases of nystagmus. The aim of the research is to determine how the nodulus and uvula control velocity storage in the vestibulo-ocular reflex (VOR) and to show how and where this control is manifested in the vestibular nuclei. This will be done in lesion, stimulation and single unit recording studies in rhesus monkeys. We also plan to determine the contribution of the inferior olive to habituation of the VOR and to plastic modification of the gain of the VOR and of OKN and OKAN. Experiments involve study of the dynamics of eye movements induced by angular rotation and surround movement before and after lesions of the nodulus and uvula, stimulation of the nodulus and uvula to show the effect on nystagmus induced by rotation, and recording of activity of single neurons in the nodulus and uvula and in the vestibular nuclei associated with animal or surround rotation. It will be determined how this activity is changed during visual suppression of the VOR or during tilts that cause nystagmus to decline rapidly or be "dumped". Extracellular activity and eye movements will be analyzed in the time domain and compared to predictions made from modelling the VOR before and after lesions. Animals will be trained with spectacles that magnify or reduce its visual field to alter the gain of the VOR plastically and effects of nodulus and uvula lesions on the plastic adaptation will be studied. This research should establish the role of the nodulus and uvula in controlling low frequency components of the VOR and show how and where in the vestibular nuclei this control is established. We also hope to determine those cells in the vestibular nuclei that are responsible for producing velocity storage and how their firing frequencies are adapted by the vestibulo-cerebellum.